Phono preamplifiers (sometimes called phono stages; phono equalisers; RIAA (Recording Industries Association of America) preamps; or RIAA equalisers) may be used in professional or domestic high fidelity systems as part of an amplifier, a general preamplifier, or as a stand-alone unit, e.g. where a turntable used for playing records has no amplifier of its own.
Phonographic audio signals, e.g. electrical signals generated by a pickup device (such as a magnetic phono cartridge) from an analogue sound storage medium (such as a record/vinyl), may undergo a pre-amplification stage in a phono preamplifier prior to a main amplification stage (following which the further amplified audio signal may be outputted, e.g. via one or more speakers). Such phonographic audio signals represent audio/sound/music recorded on the record picked up via the pickup device. A record is typically mastered to a particular record frequency response profile, i.e. a standard's frequency response reproduction curve such as the RIAA record response or the “The New Orthophonic Standard”.
The frequency response profile of FIG. 3C is typically considered as being the RIAA record output response to be equalised. Conventional phono preamplifiers seek to provide both an equalisation function as well as a (pre)amplification function of an input phono signal. The equalisation function seeks to modify the frequency spectrum of the input phono audio signal so as to equalise/compensate for the frequency response profile, i.e. ‘flattening out’ the response curve of FIG. 3C.
Conventional pre-amplification systems are not always optimal and can suffer from various issues including one or more of:
audible effects in the resultant audio output;
a complex arrangement of circuitry/components, e.g. a series or cascade of one or more active/amplification stages (to ‘fold up’) and/or one or more passive/filter stages (to ‘fold down’) regions of the record response curve at its various inflection points to flatten out/equalise the curve. Such complex arrangements of electrical components can present difficulties in determining appropriate values of the electrical components to use since the various components in the complex arrangement can interact and affect each other;
instability;
clipping and/or a low signal to noise ratio in the resultant audio output (too little gain results in a low signal to noise ratio, and too much gain results in the early onset of clipping.
The listing or discussion of any prior-published document or any background in this specification should not necessarily be taken as an acknowledgement that the document or background is part of the state of the art or is common general knowledge. One or more aspects/examples of the present disclosure may or may not address one or more of the background issues.